1. Technical Field
The present invention relates to a technology that uses a piezoelectric element for ejecting liquid such as ink.
2. Related Art
On-demand ink jet printers are roughly divided into thermal type that uses a heat generating element, and piezoelectric type that uses a piezoelectric element, as a driving element for ejecting liquid.
The piezoelectric type is more advantageous than the thermal type because the piezoelectric type does not heat ink and hence can handle various kinds of ink, and can precisely control the ejection amount of ink. In the technical field of such a piezoelectric ink jet printer, there is known a print head having a thin-film piezoelectric developed through application of micro electro mechanical systems (MEMS) technology (see Japanese Patent No. 4,078,629). The MEMS technology enables micromachining, and hence nozzles that eject ink can be highly densely arranged in the piezoelectric print head.
However, as the density of arrangement of the piezoelectric print head increases, the heat amount per unit volume increases. The increase in heat amount changes the composition of ink and the properties of ink such as viscosity, thereby increasing the risk of deterioration of ink. The increase in the risk of deterioration represents an increase in possibility that an intended product cannot be obtained due to ejection failure or deterioration of ink. This may impair the advantage of the piezoelectric print head of ejecting various kinds of liquid such as ink without applying heat to the liquid.